Composite material with controllable resonant cells

ABSTRACT

An apparatus for controlling propagation of incident electromagnetic radiation is described, comprising a composite material having electromagnetically reactive cells of small dimension relative to a wavelength of the incident electromagnetic radiation. At least one of a capacitive and inductive property of at least one of the electromagnetically reactive cells is temporally controllable to allow temporal control of an associated effective refractive index encountered by the incident electromagnetic radiation while propagating through the composite material.

FIELD

This patent specification relates generally to controllingelectromagnetic propagation for optical modulation, optical switching,or any of a variety of other useful purposes.

BACKGROUND

Devices for temporal control of the propagation of electromagneticradiation represent fundamental building blocks for many moderntechnologies. Where a single spatial dimension is involved, such as inthe propagation of a fiber optic communications signal down an opticalfiber, such control is commonly achieved by devices affecting theamplitude of the propagating light (e.g., OFF/ON). In that environment,one-dimensional electrooptical modulators are often used that are basedon electrooptic and/or magnetooptic materials such as calcite, quartz,and lithium niobate that change their refractive index responsive toapplied control signals, the materials being arranged into MachZehnderinterferometers (MZIs) or similar devices converting induced phasechanges into amplitude changes by interference effects. Otherone-dimensional electrooptical modulators include electroabsorptionmodulators variably absorbing the incident signal according to anapplied electric field, and acoustic wave modulators usinghigh-frequency sound traveling within a crystal or a planar wave guideto deflect light from one place to another. Among other issues, such aslimited power-handling ability, the above modulators each havesubstantial bandwidth limitations, e.g., practical limits to the speedat which they can vary the output signal between ON and OFF. By way ofexample, the maximum bit rate of many of the aboveelectrooptic/magnetooptic effect modulators, as well as many of theabove electroabsorption modulators, is on the order of 10-40 GHz, whilemany acoustic wave modulators have an even lower maximum bit rate.

Where two spatial dimensions are involved, e.g., in the controlledpropagation of electromagnetic wavefronts in imaging systems, devicesfor temporal control of the propagating radiation include liquidcrystal-based spatial light modulators (SLMs) and microelectromechanical(MEMs)-based SLMs, each generally providing for pixelwise amplitude orphase modulation of the propagating radiation. Among other issues, eachof these SLM types has substantial bandwidth limitations. Although someliquid-crystal SLMs may use optical control signals rather thanelectrical control signals, pixel response times are nevertheless on theorder of microseconds (binary) or milliseconds (analog). Typicalresponse times for so-called digital micromirror devices, one type ofcommercially available MEMs SLM, are on the order of microseconds. Otherissues relating to the above devices for one- or two-dimensional controlof propagating radiation include power consumption, power handlingability, size, and environmental considerations.

One particular scenario involving control of the propagation ofelectromagnetic radiation relates to coupling pump laser light into atarget device. This can be a desirable objective in many cases, such asfor optically pumping the core of an erbium-doped fiber amplifier (EDFA)using pump light from a semiconductor diode laser. In order tofacilitate higher power (e.g., one watt or greater) without damaging thesemiconductor diode laser, the facet of semiconductor diode laser isoften made relatively large. The transverse spatial modes of thesemiconductor diode laser can become quite irregular, and light can beemitted with a numerical aperture on the order of 0.3-0.4, for example.However, the EDFA core usually has a small circular mode and can onlyreceive light with a smaller numerical aperture on the order of 0.2, forexample. Coupling the pump light into the EDFA core using a taperedoptical fiber and cylindrical lens can yield relatively lowefficiencies. More generally, it may be a desirable objective to couplesource radiation from a source device having a first transverse spatialmode pattern into a target device having a second transverse spatialmode pattern that may be substantially different than the firsttransverse spatial mode pattern.

Accordingly, in relation to at least one of the above one-dimensionaland two-dimensional contexts, it would be desirable to control thepropagation of electromagnetic radiation in a manner that at leastpartially resolves one or more of the above issues. It would be furtherdesirable to provide one or more useful devices based on such controlcapabilities.

SUMMARY

In accordance with an embodiment, an apparatus is provided forcontrolling propagation of incident electromagnetic radiation,comprising a composite material having electromagnetically reactivecells of small dimension relative to a wavelength of the incidentelectromagnetic radiation. At least one of a capacitive and inductiveproperty of at least one of the electromagnetically reactive cells istemporally controllable to allow temporal control of an associatedeffective refractive index encountered by the incident electromagneticradiation while propagating through the composite material.

Also provided is a method for controlling propagation of incidentelectromagnetic radiation, comprising placing a composite material inthe path of the incident electromagnetic radiation, the compositematerial comprising resonant cells of small dimension relative to awavelength of the incident electromagnetic radiation. The method furthercomprises temporally controlling at least one of a capacitive andinductive property of at least one of the resonant cells to temporallycontrol an associated effective refractive index encountered by theincident electromagnetic radiation while propagating through thecomposite material.

Also provided is an apparatus comprising a composite material, thecomposite material comprising electromagnetically reactive cells, theapparatus further comprising means for applying incident radiation upona surface of the composite material for propagation therethrough. Theincident radiation has a wavelength substantially larger than a size ofeach of the electromagnetically reactive cells. The apparatus furthercomprises means for temporally controlling at least one of a capacitiveand inductive property of at least one of the electromagneticallyreactive cells to facilitate temporal control of an associated effectiverefractive index encountered by the incident radiation while propagatingthrough the composite material.

Also provided is an optical transistor, comprising a signal inputreceiving a signal beam, a control input receiving a control beam, and acomposite material comprising resonant cells of small dimension relativeto a wavelength of the signal beam. The composite material forms asurface receiving the signal beam from the signal input, the surfacealso receiving the control beam from the control input. At least one ofa capacitive and inductive property of the resonant cells is controlledby the control beam for controlling an effective refractive index of thecomposite material across the surface. An output signal is formed by thesignal beam upon propagation through the resonant cells as controlled bythe control beam.

Also provided is a coupling apparatus for coupling source radiation froma source device having a first transverse spatial mode pattern into atarget device having a second transverse spatial mode pattern. Thecoupling apparatus comprises a composite material having resonant cellsexhibiting a negative effective refractive index at a frequency of thesource radiation, the composite material receiving the source radiationfrom the source device. At least one of an inductive and capacitiveproperty of the resonant cells is spatially varied thereamong to causethe source radiation received from the source device to be imaged ontothe second transverse spatial mode pattern of the target device.

Also provided is a method for coupling source radiation from a sourcedevice having a first transverse spatial mode pattern into a targetdevice having a second transverse spatial mode pattern. A compositematerial is placed in a path of the source radiation, the compositematerial having resonant cells exhibiting a negative effectiverefractive index at a frequency of the source radiation. At least one ofan inductive and capacitive property of the resonant cells is spatiallyvaried thereamong to cause the source radiation received from the sourcedevice to be imaged onto the second transverse spatial mode pattern ofthe target device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an apparatus for controlling the propagation ofincident electromagnetic radiation according to an embodiment;

FIGS. 2 and 3 illustrate signal waveforms associated with the apparatusof FIG. 1 according to an embodiment;

FIG. 4 illustrates a perspective cut-away view of a resonant cellaccording to an embodiment;

FIG. 5 illustrates an apparatus for controlling the propagation ofincident electromagnetic radiation according to an embodiment;

FIGS. 6-8 illustrate top views of devices for controlling thepropagation of incident electromagnetic radiation according to one ormore embodiments;

FIG. 9 illustrates an apparatus for controlling the propagation ofincident electromagnetic radiation according to an embodiment;

FIG. 10 illustrates a coupling apparatus according to an embodiment;

FIGS. 11 and 12 illustrate transverse spatial modes of a source deviceand a target device, respectively, of FIG. 10; and

FIG. 13 illustrates a coupling apparatus according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an apparatus 100 for controlling the propagation ofincident electromagnetic radiation according to an embodiment. Apparatus100 comprises a composite material 102 comprising an arrangement ofelectromagnetically reactive or resonant cells 106 formed on one or moresubstrates, forming planar arrays 104. Apparatus 100 further comprisesan input optical system 108 receiving incident electromagnetic radiationin the form of a signal beam 110, and further receiving controlradiation in the form of a control beam 112. In the embodiment of FIG.1, the signal beam 110 and control beam 112 are one-dimensional beams oflight being provided, for example, over optical fibers to the inputoptical system 108. Apparatus 100 further comprises an output opticalsystem 118 receiving the incident electromagnetic radiation afterpropagating through the composite material 102 and emerging as an outputbeam 120.

Although propagation of optical signals (e.g., infrared, visible,ultraviolet) is discussed herein, it is to be appreciated that the scopeof the present teachings is not limited to optical signals, but rathercan include any type of electromagnetic radiation, ranging from radiofrequency radiation and microwaves to x-ray radiation, that can beintroduced into a composite material and received or collected afterpropagating through the composite material. Notably, although presentedin terms of examples in which radiation propagates into a compositematerial from one end and emerges from the other end (e.g., left toright on the drawing pages), propagation as used herein can also referto reflective cases in which radiation propagates into a compositematerial from one end and emerges from that same end.

The resonant cells 106 of composite material 102 are preferably of smalldimension (e.g., 20 percent or less) compared to a wavelength of thesignal beam 110. Unless indicated otherwise, radiation characterizedherein by a stated wavelength is presented in terms of a free-spacewavelength, with a frequency of that radiation being equal to thefree-space speed of light divided by the stated wavelength. Although theindividual response of any particular resonant cell 106 to an incidentwavefront can be quite complicated, the aggregate response the resonantcells 106 can be described macroscopically, as if the composite material102 were a continuous material, except that the permeability term isreplaced by an effective permeability and the permittivity term isreplaced by an effective permittivity. Accordingly, the term artificialmaterial or metamaterial can sometimes be used to refer to the compositematerial 102.

In the particular example of FIG. 1, each resonant cell 106 comprises asolenoidal resonator that includes a pattern of conducting materialhaving both capacitive and inductive properties. In the particularexample of FIG. 1 the conducting material is formed into a square splitring resonator pattern, but other patterns can be used including, forexample, circular split ring resonator patterns, swiss roll patterns, orother patterns exhibiting analogous properties. By way of example andnot by way of limitation, the signal beam 110 may be at a wavelength of1.55 μm, in which case the resonant cell dimension should be less thanabout 300 nm, with better performance being exhibited where thatdimension is about 150 nm or less.

The composite material 102, comprising planar arrays 104 of resonantelements 106 described herein, is generally amenable to fabricationusing photolithographic techniques and/or nanoimprint lithographytechniques. Although many different sizes are possible, the compositematerial 102 can comprise a square 1K×1K array of resonant elements 106occupying an area of about 0.3 mm×0.3 mm. The substrate material for theplanar arrays 104 should be substantially non-absorbing for light at thewavelength of the signal beam 110. Accordingly, a substrate materialcomprising GaAs or Si can be suitable for a signal beam wavelength of1.55 μm, although the scope of the present teachings is not so limited.

One salient feature of the split-ring resonator pattern of each resonantcell 106, or analogous structures according to the present teachings, isthat it brings about an inductive property and a capacitive propertythat can interact to cause a resonance condition in the presence ofelectromagnetic radiation at particular frequencies. Generally speaking,when the resonant cells 106 are placed in regular arrayed arrangementssuch as those of FIG. 1, this resonance condition is associated with acapability of neighborhoods of the resonant cells 106 to exhibitnegative effective permeability and/or negative effective permittivity.The composite material 102, or a neighborhood of resonant cells 106therein, is said to have a negative effective refractive index when theeffective permeability and effective permittivity are simultaneouslynegative. In one embodiment, the composite material 102 is formed into aso-called superlens capable of imaging with very high resolutions, evenexceeding the diffraction limitations of positive-index optical devices.

According to an embodiment, at least one of a capacitive and inductiveproperty of one or more of the resonant cells 106 is temporallycontrolled to achieve temporal control of the effective refractive indexin the neighborhood of the controlled cells. Because the resonancecondition is highly sensitive to these properties, it can be controlledand manipulated with even small changes to the local environmentaffecting these properties. In one embodiment, an electrical carrierpopulation within the substrate is externally controlled, preferably byintroducing control radiation, i.e., the control beam 112, into thatcell having a frequency different than the frequency of the signal beam110. The presence of carriers (e.g., electrons or holes) affects thecapacitive and/or inductive properties by amounts sufficient to alter,and optionally to destroy, the resonance condition so that substantialand useful control of the effective refractive index is achieved.Notably, the presence of carriers can also affect the intrinsicrefractive index of the substrate material, such as when the substratematerial comprises GaAs. Even though this intrinsic refractive indexonly changes by a very small amount, e.g., in the range of 0.1%-1%, thiscan be enough to alter the resonance condition.

Preferably, the substrate material near the conductors of the resonantcells 106 is configured and adapted to undergo carrier populationvariations responsive to receiving radiation at the frequency of thecontrol beam 112. In one embodiment, the substrate comprisessemiconductor material having a bandgap energy and a correspondingbandgap radiation frequency, wherein the control beam frequency lies ator above that bandgap radiation frequency. Control radiation is absorbedand carriers created to control the effective refractive index. Incontrast, the signal beam 110 is preferably at a frequency below thebandgap radiation frequency, and therefore the signal radiation is notabsorbed and does not appreciably affect the creation of carriers.Accordingly, propagation of the signal beam 110 is controlled by thecontrol beam 112 through variations in the effective refractive index.Notably, control of the effective refractive index can be both spatialand temporal, and therefore a wide variety of useful devices can beachieved in accordance with the present teachings, includingone-dimensional optical modulators and two-dimensional spatial lightmodulators. Spatiotemporal control of the signal beam by the compositematerial is primarily in the form of phase changes induced on thewavefronts incident to the composite material.

By way of example and not by way of limitation, a GaAs substrate as maybe used in the composite material 102 may have a bandgap energy of about1.43 eV. This corresponds to a bandgap radiation frequency correspondingto a wavelength of 867 nm. The control beam 112 should be at a frequencyhigher than the bandgap radiation frequency, i.e., at a wavelength lessthan 867 nm. The signal beam 110 should be at a frequency lower than thebandgap radiation frequency, i.e., at a wavelength greater than 867 nm.

Advantageously, the rises and falls in carrier populations of the GaAsor Si substrates responsive to changes in the control beam 112 can bevery brief, allowing for very fast temporal control of the effectiverefractive index of the composite material 102, whether it be on aspatially varying basis or uniformly across the surface as a whole. Veryfast modulation rates are therefore possible, even on the order of 100GHz where the carrier population rise and fall times are on the order ofpicoseconds.

The apparatus 100 of FIG. 1 is configured as an optical transistoraccording to an embodiment, wherein the signal beam 110 is modulated bythe control beam 112 to generate the output beam 120. In particular, theamplitude of the control beam 112 (see FIG. 1, plot 113, “CTL”) ismodulated between a (i) first value (on) that causes the compositematerial 102 to properly focus the signal beam 110 (see FIG. 1, plot111, “IN”) onto the output optical system 118 (see FIG. 1, plot 121,“OUT”), and (ii) a second value (“off”) that causes the compositematerial 102 not to properly focus the signal beam 110 onto the outputoptical system 118. Notably, any of a variety of different effectiverefractive index values and profiles can achieve the “off” state, suchas defocusing or beam redirections. In one embodiment, the “off” stateis achieved by quickly and completely destroying the resonanceconditions needed for negative effective refractive index across theentire composite material 102, and then just as quickly restoring theresonance condition for the “on” state.

Input optical system 108 and output optical system 118 comprisepositive-index imaging systems capable of achieving the functionalitiesdescribed herein. By way of example, the input optical system 108 cancomprise a fiber optic coupler that combines the signal beam 110 and thecontrol beam 112 into a single beam. The input optical system 108 canthen comprise an imaging lens that images that single beam onto thelarger area of the first planar array 104 of the composite material 102.The output optical system 118 can comprise any of a variety of opticalsystems designed to collect and guide the output beam 120. The inputoptical system 108 and output optical system 118 may be separated fromthe front and back surfaces of the composite material, respectively, bydistances on the order of 10-500 μm. Advantageously, where the compositematerial 102 comprises a “perfect lens”, the numerical aperturerequirements are very modest and low-cost light collection devices canbe used.

Practical uses for ON/OFF modulation of a constant-level signal beam, asshown in the waveforms illustrated in FIG. 1, include optical gating andwavelength conversion. FIGS. 2 and 3 illustrate alternative signalwaveforms that can be associated with the apparatus of FIG. 1 accordingto other embodiments. FIG. 2 illustrates analog modulation of aconstant-level signal beam, effectively performing an analogamplification (and wavelength conversion) of the control beam. Thisanalog implementation can be achieved using fine temporal variations ofthe control beam sufficiently precise to achieve small changes in theeffective refractive index of the composite material 102. This can becontrasted with alternative embodiments in which negative effectiveindex characteristics are entirely created and destroyed in a binarymanner. FIG. 3 illustrates level control of an analog signal beam thatcan be similarly implemented with fine temporal variations of thecontrol beam.

FIG. 4 illustrates a perspective cut-away view of a resonant cell 402that can be used in the composite material 102 of FIG. 1 according to anembodiment. In one embodiment, an outer conductor 410 and an innerconductor 412 of a solenoidally resonant structure are formed on asubstrate comprising a p-doped GaAs upper layer 404 and a p-doped GaAsmiddle layer 406, the middle layer 406 being more heavily doped than theupper layer 404. The substrate further comprises a support layer 408comprising semi-insulating GaAs, either undoped or compensated. Ametal-semiconductor interface is formed between the upper layer 404 andthe conductors 410 and 412, and carriers created by photon absorptionflow thereacross to substantially alter at least one of a capacitive andinductive property of the resonant cell 402 according to an intensity ofthe received control radiation.

Notably, the present teachings are directed to any of a variety ofmechanisms that can alter at least one of a capacitive and inductiveproperty of the resonant cell 402 responsive to control light at adifferent wavelength than the signal light. In other embodiments,n-doped material can be placed in the upper layer 404. In still otherembodiments, a single semi-insulating layer of GaAs or Si can be used,the modest carrier populations nevertheless altering the resonancecondition by amounts sufficient to change the effective refractiveindex.

FIG. 5 illustrates an apparatus 500 for controlling the propagation ofincident electromagnetic radiation according to an embodiment,comprising a composite material 502 having an arrangement of resonantcells 506 formed on one or more substrates, forming planar arrays 504.Apparatus 500 further comprises an input optical system 508 receivingincident electromagnetic radiation in the form of a signal beam 510, andfurther comprises an output optical system 518 receiving the signalradiation after propagating through the composite material 502 andemerging as an output beam 520. One or more incident control signals 512is introduced into the edges of the substrates as indicated in FIG. 5 toachieve temporal, one-dimensional control of the signal beam 510 throughsubstrate carrier population control. In one embodiment, the substratesare configured to allow the control signals 512 to laterally “flood” thesubstrate area, while in another embodiment waveguiding can be used toguide the light to the resonant cells 506. One potential advantage ofthe configuration of FIG. 5 is that the control light can be evenlydistributed on an individual basis among the planar arrays 504, incontrast to the embodiment of FIG. 1 in which subsequent layers canreceive less control light due to absorption in the prior layers. Inanother embodiment, the control light can be distributed among theplanar arrays 504 according to a desired control profile.

It is to be appreciated that FIG. 1 and FIG. 5 represent only some ofthe various ways that control light can be applied to the compositematerial according to the present teachings. The control light can beapplied from the front, from the back, from sides, etc., withoutdeparting from the scope of the present teachings. For example, FIGS.6-8 illustrate configurations for controlling signal beams (IN) withcontrol beams (CTL) using composite materials 602, 702, and 802,respectively, to produce output beams (OUT) according to still otherembodiments.

In the example of FIG. 6, the signal beam and control beam areseparately applied to a front receiving surface of the compositematerial 602 using a signal input optical system 604 and a control inputoptical system 606, respectively. The control input optical system 606is configured to cause the control beam to impinge upon the compositematerial 602 according to an intensity pattern that causes the signalbeam to be imaged onto the output optical system 608 by varying amountsaccording to a desired temporal modulation scheme. The example of FIG. 7achieves similar results using a signal input optical system 704, acontrol input optical system 706, and an output optical system 708,except that the control input optical system 706 introduces the controllight onto the back of the composite material 702. The example of FIG. 8achieves two-way switching using a signal input optical system 804 and acontrol input optical system 806 wherein, for a first state of thecontrol beam, the composite material 802 focuses the signal beam onto afirst output optical system 808, and for a second state of the controlbeam, the composite material 802 focuses the signal beam onto a secondoutput optical system 808.

FIG. 9 illustrates an apparatus for controlling the propagation ofincident electromagnetic radiation in both a spatial and temporalmanner, thereby achieving spatial light modulation functionality. Acontrol beam input system 906 images control light onto a surface of acomposite material 902 according to a desired intensity patternCTL(x,y,t) that causes a corresponding effective refractive indexprofile to be encountered by an incident signal beam 904 that, forpurposes of illustration, is shown as a coherent plane wave. Uponpropagation of the signal beam 904 though the composite material 902, itis imaged into a two-dimensional pattern OUT(x,y,t) and/or a desiredthreedimensional real image OUT(x,y,z,t) 908 in a holographic manner,i.e., according to desired spatial distribution of phase changes inducedat the composite material 902. Advantageously, very fast response timesto changes in the control signal CTL(x,y,t) are realized for very fastspatial light modulation. Many different devices for optics, imaging,and/or communications applications can be realized. In one embodiment,the intensity pattern CTL(x,y,t) comprises a binary pattern that, for afirst binary value, causes a negative effective refractive index at thatlocation, and for a second binary value, causes a positive effectiverefractive index at that location. As one of many examples, such devicescan be useful for holographic signal encryption/decryption applications.In still another embodiment, the intensity pattern is formed by twocontrol beams, a reference beam and an object beam, each at the controlradiation frequency, the reference beam and the object beam beingdirected toward the front surface of the composite material at differentangles similar to the way holograms are recorded onto film emulsions,whereby the resulting intensity pattern comprises a hologram-likeinterference pattern.

FIG. 10 illustrates a coupling apparatus for coupling source radiationfrom a source device (e.g., a pump laser 1004) into a target device 1006according to an embodiment, the coupling apparatus comprising acomposite material 1002. In this example, the pump laser 1004 has anemitting facet 1008 and emits pump light according to an irregulartransverse spatial mode pattern, as conceptualized in FIG. 11 showing afirst transverse spatial mode pattern 1102, whereas the target device1006 comprises a receiving surface 1010 and operates according to asecond transverse spatial mode pattern 1202 shown in FIG. 12. By way ofexample, the target device 1006 may be a core-pumped EDFA, while thepump laser 1008 may comprise a semiconductor diode laser, although thescope of the present teachings is not so limited.

According to an embodiment, the composite material 1002 is configured tohave a spatial effective refractive index pattern that images the firsttransverse spatial mode pattern 1102 onto the second transverse spatialmode pattern 1202. In one embodiment, this effective refractive indexpattern can be statically achieved, i.e., according to static resonantcell parameter variations (e.g., material, shape, size) across thecomposite material. In another embodiment, the effective refractiveindex pattern is spatially and temporally controlled by spatiotemporalcarrier population control in the substrate.

FIG. 13 illustrates a coupling apparatus for coupling source radiationfrom a source device (e.g., a pump laser 1304) into a target device 1306according to an embodiment, the coupling apparatus comprising acomposite material 1302, a control input optical system 1306, a sensor1310, and a feedback control processor 1312. The control input opticalsystem 1306 images control light onto a surface of a composite material1302 according to a desired intensity pattern CTL(x,y,t) designed tocause the composite material 1302 to image a first transverse spatialmode pattern of the pump laser 1304 a second transverse spatial modepattern of a target device 1308. The sensor 1310 is configured to sensea coupling efficiency by sensing, for example, an intensity of an outputproduced by the target device 1308. A feedback control processor 1312 isconfigured to dynamically modify the intensity pattern CTL(x,y,t) in amanner that improves or optimizes the coupling efficiency.

Whereas many alterations and modifications of the embodiments will nodoubt become apparent to a person of ordinary skill in the art afterhaving read the foregoing description, it is to be understood that theparticular embodiments shown and described by way of illustration are inno way intended to be considered limiting. By way of example, while someembodiments supra are described in the context of negative-indexmaterials, the features and advantages of the embodiments are readilyapplicable in the context of other composite materials. Examples includeso-called indefinite materials (see WO 2004/020186 A2) in which thepermeability and permittivity are of opposite signs.

By way of further example, it is to be appreciated that the compositematerial 102 of FIG. 1 represents a simplified example for clarity ofdescription, showing only a single set of planar arrays 104 alignedalong a direction of propagation. In other embodiments a second set ofplanar arrays can be provided perpendicular to the first set of planararrays 104 for facilitating negative effective permittivity and/ornegative effective permeability for more directions of propagation. Instill other embodiments, a third set of planar arrays can be providedperpendicular to both the first set and second sets of planar arrays forfacilitating negative effective permittivity and/or negative effectivepermeability for even more directions of propagation. It is to befurther appreciated that one or more additional sets of composite and/orcontinuousmaterial planes can be placed between the planar arrays 104without departing from the scope of the present teachings. By way ofexample, planar arrays consisting of vertical conducting wires on adielectric support structure can be interwoven with planar arrays 104 toprovide a more negative effective permittivity for the overall compositematerial 100. It is to be further appreciated that the number ofresonant cells 106 on the planar arrays 102 can be in the hundreds,thousands, or beyond depending on the overall desired dimensions and thedesired operating wavelength.

By way of further example, the temporally controlled resonant cells canbe implemented on only a portion of a larger composite material, or inassociation a subset of the possible directions of an anisotropiccomposite material, or interleaved in one or more directions with acontinuous material as part of a larger composite material, withoutdeparting from the scope of the embodiments. By way of still furtherexample, electrical carrier injection into the resonant cells, ifachievable without destroying the resonance conditions in other ways, iswithin the scope of the present teachings. By way of still furtherexample, although devices according to the present teachings can providefor very fast temporal control, such control can of course be providedin a very slow manner to provide static devices having fixed controlbeams, and/or quasi-static devices having control beams that are alteredvery rarely, e.g. once every day, month, or year in a manner similar tothe way flashable memory devices are controlled. Thus, reference to thedetails of the described embodiments are not intended to limit theirscope.

1-36. (canceled)
 37. An optical transistor, comprising: a signal inputreceiving a signal beam; a control input receiving a control beam; and acomposite material comprising resonant cells of small dimension relativeto a wavelength of the signal beam, the composite material forming asurface receiving the signal beam from said signal input and receivingthe control beam from said control input, at least one of a capacitiveand inductive property of said resonant cells being controlled by saidcontrol beam for controlling an effective refractive index of saidcomposite material across said surface, an output signal being formed bysaid signal beam upon propagation through said resonant cells ascontrolled by said control beam.
 38. The optical transistor of claim 27,wherein said effective refractive index of said resonant cells acrosssaid surface is controlled according to an intensity pattern of saidcontrol beam across said surface.
 39. The optical transistor of claim38, each of said resonant cells comprising at least one electricalconductor and a substrate, said intensity pattern controlling saideffective refractive index by affecting carrier populations in saidsubstrates near said electrical conductors of said resonant cells. 40.The optical transistor of claim 39, each of said substrates comprising asemiconductor material having a bandgap energy, wherein said signal beamcomprises radiation at a first frequency below a bandgap radiationfrequency corresponding to said bandgap energy, and wherein said controlbeam comprises radiation at a second frequency above said bandgapradiation frequency.
 41. The optical transistor of claim 40, furthercomprising an output location receiving a variable proportion of saidoutput signal according to said intensity pattern of said control beam,wherein said effective refractive index is controllable across saidsurface between a first value less than zero and a second value greaterthan zero according to said intensity pattern of said control beam. 42.The optical transistor of claim 41, said variable proportion beingcontinuously controllable between a lower proportion and an upperproportion, wherein said optical transistor provides for analogmodulation of said signal beam by said control beam.
 43. The opticaltransistor of claim 41, said variable proportion being controllable inbinary manner between an off state and an on state, said opticaltransistor providing for on-off switching of said signal beam by saidcontrol beam.
 44. The optical transistor of claim 40, further comprisinga first output location receiving a first variable proportion of saidoutput signal according to said intensity pattern of said control beamand a second output location receiving a second variable proportion ofsaid output signal according to said intensity pattern of said controlbeam, said optical transistor providing for directional switching ofsaid signal beam according to said control beam.
 45. A couplingapparatus for coupling source radiation from a source device having afirst transverse spatial mode pattern into a target device having asecond transverse spatial mode pattern, comprising a composite materialhaving resonant cells exhibiting a negative effective refractive indexat a frequency of said source radiation, the composite materialreceiving the source radiation from the source device, wherein at leastone of an inductive and capacitive property of said resonant cells isspatially varied thereamong to cause the source radiation received fromthe source device to be imaged onto the second transverse spatial modepattern of the target device.
 46. The coupling apparatus of claim 45,wherein said source radiation comprises pump light at an energy ofgreater than one watt, wherein said source device comprises a pumplaser, and wherein said target device comprises an optically pumpeddevice.
 47. The coupling apparatus of claim 45, wherein said at leastone of an inductive and capacitive property is temporally controllableto allow temporal control of an effective refractive index associatedwith the resonant cells.
 48. The coupling apparatus of claim 47, each ofsaid resonant cells comprising at least one electrical conductor and asubstrate, wherein said temporal control is achieved by control of acarrier population within said substrate.
 49. The coupling apparatus ofclaim 48, said substrate comprising a semiconductor material having abandgap energy, said source radiation being in a first frequency rangebelow a bandgap radiation frequency corresponding to said bandgapenergy, wherein said carrier population is controlled by introducingcontrol radiation into said resonant cells, said control radiation beingin a second frequency range above said bandgap radiation frequency. 50.The coupling apparatus of claim 49, said resonant cells forming asurface receiving said source radiation, wherein said control radiationis imaged onto said surface by a control radiation imaging device toform a two-dimensional intensity pattern thereon, said imaging of saidsource radiation onto said second transverse spatial mode pattern ofsaid target device being implemented according to said two-dimensionalintensity pattern.
 51. The coupling apparatus of claim 50, furthercomprising a feedback control device detecting a coupling efficiencybetween said source laser and said target device, said feedback controldevice interacting with said control radiation imaging device tooptimize said coupling efficiency by dynamic adjustment of saidtwo-dimensional intensity pattern.
 52. A method for coupling sourceradiation from a source device having a first transverse spatial modepattern into a target device having a second transverse spatial modepattern, comprising placing a composite material in a path of the sourceradiation, the composite material having resonant cells exhibiting anegative effective refractive index at a frequency of said sourceradiation, wherein at least one of an inductive and capacitive propertyof said resonant cells is spatially varied thereamong to cause thesource radiation received from the source device to be imaged onto thesecond transverse spatial mode pattern of the target device.
 53. Themethod of claim 52, wherein said source radiation comprises pump lightat an energy of greater than one watt, wherein said source devicecomprises a pump laser, and wherein said target device comprises anoptically pumped device.
 54. The method of claim 52, further comprisingtemporally controlling said inductive and/or capacitive property amongsaid resonant cells to facilitate temporal control of an effectiverefractive index associated therewith.
 55. The method of claim 54, eachof said resonant cells comprising at least one electrical conductor anda substrate, wherein said temporally controlling comprises controlling acarrier population within said substrate.
 56. The method of claim 55,said substrate comprising a semiconductor material having a bandgapenergy, said source radiation being in a first frequency range below abandgap radiation frequency corresponding to said bandgap energy,wherein said controlling a carrier population comprises introducingcontrol radiation into said resonant cells, said control radiation beingin a second frequency range above said bandgap radiation frequency. 57.The method of claim 56, said resonant cells forming a surface receivingsaid source radiation, wherein said introducing control radiationcomprises imaging the control radiation onto the surface to form atwo-dimensional intensity pattern thereon, said imaging of said sourceradiation onto said second transverse spatial mode pattern of saidtarget device being implemented according to said two-dimensionalintensity pattern.
 58. The method of claim 57, further comprising:detecting a coupling efficiency between said source laser and saidtarget device; and dynamically adjusting said two-dimensional intensitypattern device to improve said coupling efficiency.